State library

Can I use it in Flot?

preview build err: 
```
# sigint.ca/slice/cmd/preview
.\main.go:116: w.Events undefined (type screen.Window has no field or method Events)
.\main.go:117: use of .(type) outside type switch
.\main.go:140: too many arguments in call to w.Upload
.\main.go:143: undefined: screen.UploadedEvent
```